The Golden Temple, constructed in the 16th century, is so sacred to Sikhs because it is considered to be the main site of pilgrimage for the faith.

The mosque tweet has therefore enraged many on social media, particularly British Sikhs.

Bhai Amrik Singh, chairman of the Sikh Federation, said: “This was a major gaffe by a top civil servant and totally unacceptable.

He added: “In our view, a public apology and admitting the mistake is not enough. What we need is a commitment from the UK Government and senior civil servants to root out such ignorance and discrimination or we will continue to face hate, abuse and threats of violence.”

The Queen had visited the site in 1997, 13 years after a deadly and extremely controversial assault by the Indian army took place, which was aimed at expelling armed separatists who wanted a separate Sikh homeland.

Jeremy Corbyn has vowed that if he were to become Prime Minister he would launch a probe to investigate Britain’s role during the raid in the party’s next manifesto.

Jeremy Corbyn speaks during an interview in London, April 20,2018Credit:
Anadolu Agency

The scale of the UK’s involvement in the assault, which reportedly left thousands dead, is currently under intense scrutiny, making the blunder even more awkward for Sir Simon.

Addressing a Sikhs for Labour meeting in Watford, Mr Corbyn remarked: “You can be very sure that, whenever the election comes, it will be in the next manifesto … it’s a commitment that’s going to be there and we will honour that commitment.”

Sir Simon has been on a visit to the Northern Indian city of Chandigarh, where he has been meeting students and politicians.

Dr Jasjit Singh, a researcher at Leeds University, questioned if the diplomat had been thinking of the Golden Mosque in Rochdale, which is an actual place of Muslim worship.